4.58pm: Here is a summary of developments on a day that was dominated by the news of the death of two foreign journalists in Homs. They were among 80 people reportedly killed in the city today.

Syria

• Two foreign journalists – Marie Colvin of the Sunday Times and French photographer Rémi Ochlik – died in Homs this morning when a building being used as a makeshift press centre was shelled. Several other journalists are said to have been injured.

• Tributes have been pouring in, including from Rupert Murdoch, head of News Corporation, which is the ultimate owner of the Sunday Times, and fellow journalists, including the BBC's Jeremy Bowen, Channel 4's Lindsey Hilsum and ITN's international editor Bill Neely.

• The UK foreign secretary also paid tribute to the pair and condemned "the Assad regime's despicable campaign of terror". France stepped up its criticism of the French regime, with President Nicolas Sarkozy saying "That's enough now, the regime must go."

• Activists said 80 people were killed in Babr Amr today, including Colvin and Ochlik. More than 60 bodies, both rebel fighters and civilians, were recovered from one area after an afternoon bombardment, adding to 21 killed earlier in the day, they said. The campaign group Avaaz said seven unarmed activists, including one doctor, were assassinated in cold blood while trying to bring medical supplies into Homs. The reports of activists cannot be independently verified.

• Rami al-Sayed, a Syrian citizen journalist who provided live video streams from Homs, has also been killed. He was hit during the shelling of Bab Amr yesterday and died some hours later. His videos – more than 800 of them – were posted under the name "syriapioneer".

• The opposition Syrian National Council (SNC) says it is coming to the view that military intervention in Syria is the only solution. "We are really close to seeing this military intervention as the only solution. There are two evils, military intervention or protracted civil war," Basma Kodmani, a senior SNC official, told a press conference in Paris. But Damascus-based opposition group "Building the Syrian State" said military intervention would divide the Syrian people. It called for dialogue with the regime during a transitional period in which power would be share.

Yemen

• Turnout for yesterday's one-candidate presidential poll in Yemen hit an average of 60% across the country, according to a monitor quoted by AFP, though it was lower in the south.

Egypt

• The verdict - and sentence if there is a guilty verdict - in the trial of former Egyptian President Hosni Mubarak will be delivered on June 2, the judge said today. . He is charged with charged with ordering the killing of protesters in the uprising that swept him from power and also with corruption.

Rami al-Sayyed had been known as Rami Abou Maryam and Syria Pioneer. He volunteered his time in Baba Amr as an undercover citizen journalist. He was one of the first activists who risked their lives and braved sniper bullets to film the protests in Homs.

Rami also set up a channel to livestream the anti-regime demonstrations and the army's assaults on the city. Rami never admitted he was the one behind the channel but whenever his colleagues told me he is "out" or "busy" I was sure to find a live feed on his channel.

Interviews with Rami were often too close for comfort. Sounds of gunfire and explosions are common background noise on calls with activists in Homs (and elsewhere in Syria) but on calls with Rami I often heard shells whizzing by. On my last call with him he was speaking from an activist hide out. He went there to upload videos of a family that had been buried in the rubble of a collapsed building. All members were dead. "We plead to humanitarian organizations to provide safe passage for the women and children. Leave us men to our fate. But for the sake of humanity let these women and kids go far from here." I didn't know what to tell him.

The humanitarian organizations are fully aware of the situation. They will not send aid workers as long as bullets were flying. I thanked Rami for taking the time to talk to me and hung up. When I woke up today I found a live feed from Bab Amro. It was Syria Pioneer's channel and it showed the army's brutal shelling of Homs into the eighteenth day. The feed stopped broadcasting at around 11:00 (local). Later in the evening I called another activist in Baba Amr as Rami was not online. The activist relayed to me the sad news that Rami was critically wounded by shrapnel and that he was receiving treatment in the field hospital. A few hours later Rami passed way.

The barrages marked an intensification of a nearly three-week offensive to crush resistance in Homs, one of the focal points of a nationwide uprising against Assad's 11-year rule and its ferocity has caused international outrage.

More than 60 bodies, both rebel fighters and civilians, were recovered from one area of Homs' Babo Amro neighbourhood after an afternoon bombardment, adding to 21 killed earlier in the day, activists said.

"President Assad wants to finish the Homs situation by Sunday to prepare for the constitutional referendum. Then he will turn to Idlib," a Lebanese official who is close to the Syrian government told Reuters in Beirut.

Photograph: Fayez Nureldine/AFP/Getty Images

4.10pm: Saudi Arabia's King Abdullah (pictured left) has told Russian President Dmitry Medvedev that any dialogue about the crisis engulfing Syria is futile, in the wake of Russia's veto of a UN security council resolution. According to the Saudi state news agency SPA, the Saudi monarch said during a telephone conversation with Medvedev:

As for now, any discussion about the situation (in Syria) would be fruitless ... It would have been better if our Russian friends coordinated with the Arabs before using the veto in the security council ...

We cannot abandon our religious and moral position towards the situation in Syria.

It is unclear what alternative - if any - Abdullah is proposing. Russia has called for dialogue between the two sides in Syria but the opposition says it cannot negotiate with the regime as things stand. The most high profile opposition group (if not necessarily the most representative), the Syrian National Council, has said it is close to seeing military intervention as "the only solution".

3.45pm: The campaign group Avaaz claims seven activists were killed today while trying to take medical supplies into Homs today.

Executive director Ricken Patel said:

Seven unarmed activists, including one doctor, were assassinated in cold blood today while trying to bring medical supplies into Homs. They join the roll call of brave citizens, medical workers and journalists murdered by a regime that has gone beyond all limits of brutality. An urgent humanitarian ceasefire must be imposed in Homs and other cities now so that medical supplies can be brought in. This must be at the top of the Tunisia agenda when they meet on Friday.

According to Avaaz citizen journalists, there is now:

• Only one field hospital in Baba Amr and there are not enough doctors or nurses to help the wounded. Doctors are exhausted, after 19 days of non-stop emergencies.

• A chronic lack of medicines, scissors are having to be used to operate on people, flames to sterilise their tools and there is a lack of painkillers and antibiotics in the city.

• In some locations only a vet is available to assist people and in one other place a builder with two weeks first aid training is assisting people.

• Ambulances cannot move in Baba Amr and the wounded are not allowed to leave.

3.17pm: A video (above) purporting to show shelling in the Baba Amr district of Homs today has been posted on Youtube. Like the livestream, it has been posted under the account of citizen journalist Rami al-Sayed (aka "syriapioneer"), who was killed in Homs on Tuesday.

The Local Co-ordination Committees activist group says 20 people have been killed in Homs today, including Marie Colvin and Rémi Ochlik. It says another 10 people have been killed across the rest of Syria: five in Hama, two in Idlib, and one in each of Deraa and Aleppo. In Aleppo, the man who was killed is named as Naser al-Dean Brhek, described as a Kurdish leader.

3.04pm: Marie Colvin's last report for the Sunday Times has now been moved outside the paywall. She writes:

I entered Homs on a smugglers' route, which I promised not to reveal, climbing over walls in the dark and slipping into muddy trenches. Arriving in the darkened city in the early hours, I was met by a welcoming party keen for foreign journalists to reveal the city's plight to the world. So desperate were they that they bundled me into an open truck and drove at speed with the headlights on, everyone standing in the back shouting "Allahu akbar" — God is the greatest. Inevitably, the Syrian army opened fire.

When everyone had calmed down I was driven in a small car, its lights off, along dark empty streets, the danger palpable. As we passed an open stretch of road, a Syrian army unit fired on the car again with machineguns and launched a rocket-propelled grenade. We sped into a row of abandoned buildings for cover.

The scale of human tragedy in the city is immense. The inhabitants are living in terror. Almost every family seems to have suffered the death or injury of a loved one.

2.54pm: The video above is said to show a demonstration today outside the main library of Aleppo university in Syria.

Aleppo has been relatively quiet until recently. Yesterday, security forces reportedly opened fire inside the campus while confronting a protest by about 2,500 students at the science faculty.

2.37pm: Impressive. Less than 24 hours after citizen journalist Rami al-Sayed (aka "syriapioneer") was killed in Homs, his friends have resumed the video live-streaming (above).

2.29pm: The last day of ex-president Mubarak's seven-month trial in Egypt seems to turning into an anticlimax. Asked if he wanted to say anything to the court, Mubarak told the judge: "I have no comment. What the lawyer said is enough."

AP reports that Mubarak's defence team claims he is still president, and thus can only be tried for treason or in a special court. The prosecution is asking for the death sentence and the judge is expected to decide later in the session on a date for the verdict.

Meanwhile, a report from parliament to the court suggests the ailing ex-president could be moved from International Medical Center, where he is currently held, to the hospital in Tora prison. The report says the prison hospital has the necessary facilties to treat him.

2.16pm: While the Syrian National Council says that it is coming to the view that military intervention in Syria "is the only solution", that is far from a universal view amongst the opposition.

Members of the "Building the Syrian State" group who are based in Syria but visiting Europe to drum up support for the opposition movement within Syria (and to show that there is political opposition movement within the country), gave a very different message at a meeting hosted by by the Council of Arab and British Understanding (Caabu) in London today.

Mouna Ghanem, ex-regional director for the United Nation Fund for Women (Unifem), said:

I don't think military intervention will help protect civilians in the country. It might create divisions in Syrian society. If there is military intervention some of the people will fight with the coming soldiers and others will be fighting against this and this would put the country in a very dangerous situation.

Louay Hussein, who spent seven years in prison between 1984 and 1991 and is president of the opposition group, described Britain's approach to the crisis as "rational", comparing it favourably to France, suggesting he finds Nicolas Sarkozy's approach too belligerent. He said the answer lay in dialogue between the opposition and the current regime during an interim period in which they would share power and said the international community should be focusing on bringing the two sides together.

Hussein said that he had not participated in the government's "national dialogue" because it didn't represent a genuine dialogue.

"The solution we accept is not just a dialogue but negotiations for a transitional period during which we share power."

He said that that Assad could be involved in this process if necessary.

"It's not going to stop us negotiating with him if it will reach a solution. Unfortunately, solving the crisis still requires his will to solve it ... The question of whether Bashar al-Assad is involved or not is a question the parties who decide to negotiate will have to make".

But Hussein confirmed the external impressions of an opposition that is fractured and lacking ideas:

There is no serious sense that the regime is ready to, one, enter a political process, and, two, the regime is near collapse. We need the Syrian opposition to be a bit more brave, to come up with solutions and we need the same from the international community ...

Unfortunately, the relationships between different opposition groups are not very good and very encouraging. Regardless of the reasons why, the opposition is weak. The reality is that the Syrian opposition is unable to lead this historic moment and come up with particular solutions at this very important time in Syria. The best relations we have are with independent groups you don't hear a lot about in the media, not the SNC, they are small civil society and political initiatives.

2.02pm: The authorities in Damascus say they did not know that Marie Colvin and Rémi Ochlik were in Syria, al-Jazeera reports.

"The authorities had no information that the two journalists had entered Syrian territory," information minister Adnan Mahmoud told AFP news agency.

1.27pm: Lindsey Hilsum of Channel 4 News said she has lost a dear friend and the world has lost a rare breed of "old-fashioned eye-witness" reporters.

A tearful Hilsum said she spoke to Colvin just yesterday and she had told her privately that Homs "was the worst we've ever seen" in all her years reporting from the frontline and she cared passionately about getting that communicated to the rest of the world.

"To see what she saw and remember she lost on eye in a conflict in Sri Lanka. For her to say this is the worst she has ever seen...

"I think what was exceptional about Marie was that she was so incredibly brave and went to places that most of the rest of us wouldn't go to and stayed longer than us.

"She was that old-fashioned kind of journalist who would to be an eyewitness, not an 'in-and-out, firefighter'. There are not many people who do that and you just have to look at her last dispatch this weekend to see the quality of the reporting, the compassion, the anger and also the objectivity."

In her final dispatch for the Sunday Times, Colvin spoke of the citizens of Hom living "in fear of a massacre". She wrote of residents begging her to tell the world to help them and to get the bombing stopped. "The scale of human tragedy in the city is immense. The inhabitants are living in terror. Almost every family seems to have suffered the death or injury of a loved one."

Hilsum said: "Marie felt very strongly about the importance of reporting, but it didn't blind her to the faults and weaknesses [of activists]. She had an incredible ability not to take sides and there aren't a lot of journalists around like that."

Asked what impact her reporting had, Hilsum said: "None of us ever really know what impact our journalism has. Marie didn't have any illusions about that. She felt reporting was important in itself. She would say she wanted to to do it so 'nobody can say we didn't know what was happening in Homs'.

Hilsum described Colvin as the "most utterly brilliant" person to know who gave others courage and had an incredible zest for life when back in London. She always looked glamorous back at home, dressing in a black cocktail dress and a special eye-patch with rhinestones for dinner parties. "She was an amazing character."

"She just got on with it. She really cared about situations. I really felt that when I spoke to her yesterday".

1.15pm: The Guardian's Syria interactive has been updated to show where the two journalists were killed.

Syria

• Two foreign journalists – Marie Colvin of the Sunday Times and French photographer Rémi Ochlik – died in Homs this morning when a building being used as a makeshift press centre was shelled. Several other journalists are said to have been injured.

• Tributes have been pouring in – including one from Britain's foreign secretary, William Hague, and another from Rupert Murdoch, head of News Corporation, which is the ultimate owner of the Sunday Times.

• Rami al-Sayed, a Syrian citizen journalist who provided live video streams from Homs, has also been killed. He was hit during the shelling of Bab Amr yesterday and died some hours later. His videos – more than 800 of them – were posted under the name "syriapioneer".

• The opposition Syrian National Council (SNC) says it is coming to the view that military intervention in Syria is the only solution. "We are really close to seeing this military intervention as the only solution. There are two evils, military intervention or protracted civil war," Basma Kodmani, a senior SNC official, told a press conference in Paris.

Yemen

• Turnout for yesterday's one-candidate presidential poll in Yemen hit an average of 60% across the country, according to a monitor quoted by AFP, though it was lower in the south.

Egypt

• Today is expected to be the final day of ex-president Hosni Mubarak's trial in Egypt, though a verdict is unlikely to be announced for some time.

In the clinic, if you can even call it that - it's an apartment with two operating tables and a dentist and a doctor - ther was a tiny baby, well one-year-old, naked, hit in the left chest. The doctors just said 'We can't do anything and we had to watch the baby, little tummy, desperate for breath, die.

"I am deeply saddened and shocked by the tragic news that Marie Colvin and French photographer Rémi Ochlik have been killed while reporting, with great bravery, from Homs in Syria. I offer my heartfelt condolences to their families, friends and colleagues as they face this devastating loss.

Marie Colvin embodied the highest values of journalism throughout her long and distinguished career as a foreign correspondent for the Sunday Times. For years she shined a light on stories that others could not and placed herself in the most dangerous environments to do so, including suffering injuries while reporting in Sri Lanka. She was utterly dedicated to her work, admired by all of us who encountered her, and respected and revered by her peers. Her tragic death is a terrible reminder of the risks that journalists take to report the truth.

It is also a terrible reminder of the suffering of the Syrian people – scores of whom are dying every day. Marie and Remi died bringing us the truth about what is happening to the people of Homs. Governments around the world have the responsibility to act upon that truth – and to redouble our efforts to stop the Assad regime's despicable campaign of terror in Syria."

12.36pm: In an email to staff today, Rupert Murdoch, boss of News Corporation, the ultimate owner of the Sunday Times, described Marie Colvin as "one of the most outstanding foreign correspondents of her generation":

It is with great sadness that I have learned of the death of Marie Colvin, one of the most outstanding foreign correspondents of her generation, who was killed in Homs in Syria today while reporting for the Sunday Times.

She was a victim of a shell attack by the Syrian army on a building that had been turned into an impromptu press centre by the rebels. Our photographer, Paul Conroy, was with her and is believed to have been injured. We are doing all we can in the face of shelling and sniper fire to get him to safety and to recover Marie's body.

Marie had fearlessly covered wars across the Middle East and south Asia for 25 years for the Sunday Times. She put her life in danger on many occasions because she was driven by a determination that the misdeeds of tyrants and the suffering of the victims did not go unreported. This was at great personal cost, including the loss of the sight in one eye while covering the civil war in Sri Lanka. This injury did not stop her from returning to even more dangerous assignments.

Our immediate thoughts are with her family.

12.30pm: The Sunday Times editor John Witherow has described Marie Colvin as an "extraordinary figure in the life of the Sunday Times" in a staement:

I want to report with great shock the sad news of the death of Marie Colvin in Syria today. We have reliable reports that Marie was killed in Homs while covering the devastating bombardment by the Syrian army. She was with Paul Conroy, the freelance photographer, who was injured in the attack. We do not know the extent of his wounds but the early reports suggest he is not too seriously hurt. We are doing what we can to get him to safety and to recover Marie's body.

Marie was an extraordinary figure in the life of the Sunday Times, driven by a passion to cover wars in the belief that what she did mattered. She believed profoundly that reporting could curtail the excesses of brutal regimes and make the international community take notice. Above all, as we saw in her powerful report last weekend, her thoughts were with the victims of violence.

Throughout her long career she took risks to fulfil this goal, including being badly injured in Sri Lanka. Nothing seemed to deter her. But she was much more than a war reporter. She was a woman with a tremendous joie de vivre, full of humour and mischief and surrounded by a large circle of friends, all of whom feared the consequences of her bravery.

Marie was recruited to the Sunday Times more than a quarter of a century ago by David Blundy, her predecessor as Middle East correspondent, who was himself killed in El Salvador in 1989. It shows the risks that foreign correspondents are prepared to take in the pursuit of the truth.

He said she wanted to keep going as a foreign correspondent so that no-one had the excuse to say "I did not know" of the horrors in the world.

Neely, who returned from Syria 10 days ago, worked with Colvin many times and today described her death as a great loss. He said she was not fearless, as so many say, but she was brave. "She said we had to keep our nerve and keep reporting war. Why? So that no-one would have an excuse to say "I did not know"."

He added: "She took the deep breath over and over and plunged herself in, as deep as she could,to scoop out the nuggets we all need to know. And we were all,as a people,better for her."

Neely said "her final dispatch" in last weekend's Sunday Times "was as deep as they come, in the 'widow's cellar' where women and children cower from Assad's assault and death feels imminent." He added: "At a time when journalists are being examined as never before, it's time to acknowledge someone who made a difference, a moral difference, to our country and our lives. That was Marie."

"She wanted her words from Syria to reach as wide an audience as possible and was frustrated at the "paywall" that prevented her article for the Sunday Times being widely available on the internet.

Neely continued: "The great journalist Martha Gellhorn wrote, 'All my reporting life, I have thrown small pebbles into a very large pond, and have no way of knowing whether any pebble caused the slightest ripple. I don't need to worry about that. My responsibility was the effort.' Marie threw pebbles and caused ripples. On Monday I sent her a message; 'Bravo Marie.Keep your head down.' This morning I looked at the video of her body in a house in Homs. Her head down. Her voice silenced. And we are all the poorer for that. Bless you Marie."

Regular Syria watchers will recognise one of the doctors in the video as Mohammad al-Mohammad who has featured in a number of videos from a makeshift hospital, highlighting the plight of people in Homs and appealing for assistance.

Rémi Ochlik, 28, was an award-winning French photojournalist, considered one of the biggest talents of a new generation of young news photographer-reporters.

Born in Lorraine in the east of France, he said he had always wanted to be a war photographer and made his name aged 20 while he still in photography college in Paris when he went to Haiti in 2004 to document the riots and bloody conflict surrounding the fall of the president Jean-Bertrand Aristide.

He won a prestigious award for young reporters and later founded his own photography agency, IP3 Press. In 2008, he covered war in the Democratic Republic of Congo and returned to Haiti in 2010 to document the cholera epidemic.

11.32am: The online campaign group, Avaaz, says its staff spoke to Rémi Ochlik hours before he was killed.

It says:

The house that the journalists were based in was a well known temporary press centre in Homs which sat next door to a hospital. They were directly targeted. When shelling started abruptly this morning, without warning, it was in contravention of all humanitarian law.

The group quotes one of its citizen journalists in Homs, Abu Bakr, as saying:

I left the house after it got struck and headed to a house across the street. The shelling continues and the bodies of the journalists are still on the ground. We can't get them out because of the intensity of the shelling even though we're only a few metres away from them.

11.01am: The French government has named the two journalists killed in Syria as Marie Colvin of the Sunday Times and French photographer Rémi Ochlik.

A BBC video shows what is believed to be Marie Colvin's last report from Homs where she talks about witnessing the death of a baby hit during the shelling and ends with the words: "It is just unrelenting".

At a memorial service in 2010 for another journalist killed in a war zone, she said:

Despite all the videos you see from the Ministry of Defence or the Pentagon, and all the sanitised language describing smart bombs and pinpoint strikes… the scene on the ground has remained remarkably the same for hundreds of years. Craters. Burned houses. Mutilated bodies. Women weeping for children and husbands. Men for their wives, mothers children.

Our mission is to report these horrors of war with accuracy and without prejudice.

We always have to ask ourselves whether the level of risk is worth the story. What is bravery, and what is bravado?

There was a very fierce battle between the guards on our convoy and an armed movement that is very determined to stop these elections which will lead to a peaceful transfer of power.

We took cover inside the polling station but there was very heavy gunfire that moved closer and closer.

It lasted about 45 minutes to an hour until a detachment of the army came and pushed them back.

10.00am: The opposition Syrian National Council (SNC) says it is coming to the view that military intervention in Syria is the only solution.

"We are really close to seeing this military intervention as the only solution. There are two evils, military intervention or protracted civil war," Basma Kodmani, a senior SNC official, told a press conference in Paris which is reported by Reuters.

The SNC will also urge Egypt, at a "Friends of Syria" meeting due to be held in Tunis on Friday, to restrict access to the Suez Canal to any ships carrying weapons to the Syrian regime.

9.45am: A grim report from Reuters about young men in Idlib province being rounded up and shot in cold blood:

Syrian troops and militiamen loyal to President Bashar al-Assad chased, captured and then shot dead 27 young men in three northern villages, an opposition activists' group said on Wednesday.

The men, all civilians, were mostly shot in the head or chest on Tuesday in their homes or in streets in the villages of Idita, Iblin and Balshon in Idlib province near the border with Turkey, the Syrian Network for Human Rights said.

"Military forces chased civilians in these villages, arrested them and killed them without hesitation. They concentrated on male youths and whoever did not manage to escape was to be killed," the organisation said in a statement.

"Responsibility for this massacre lies with the general commander of the military and armed forces, Bashar al-Assad," the statement said, adding that only one youth survived the shootings.

Several YouTube videos taken by local activists in Idlib, which could not be independently confirmed, showed bodies of young men with bullet wounds lying in streets and in houses.

9.19am: Rami al-Sayed, a citizen journalist who provided live video streams from Homs, was hit during the shelling of Baba Amr yesterday and died some hours later.

Dr Mohammad al-Mohammed, who has appeared in numerous videos on the Gurdian's live blog, is quoted as saying: "Rami was killed because he was broadcasting real footage from Baba Amr. "Rami was killed because he was recording the truth."

It says one American and one French journalist were with activists in a building which was shelled this morning. A photographer was reportely injured.

8.51am: (all times GMT) Welcome to Middle East Live. Here is a roundup of the situation this morning:

Syria

• The US says it "may have to consider additional measures" regarding Syria, though it does not want to take actions that would "contribute to the further militarisation" of the country. Activists said more than 100 people were killed in Syria yesterday.

• A video has been posted on the internet in support of claims that 500 government troops have defected to the Free Syrian Army.

Yemen

• Nine people are reported killed during yesterday's single-candidate presidential election in Yemen. Turnout was low in the south of the country where separatist sentiment is strong.

Egypt

• Today is the last day of ex-president Mubarak's trial in Egypt, though no verdict is expected until later.